libavcodec/amr.h

   1 /*
   2  * Shared functions between AMR codecs
   3  *
   4  * Copyright (c) 2010 Marcelo Galvao Povoa
   5  *
   6  * This file is part of Libav.
   7  *
   8  * Libav is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * Libav is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with Libav; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #ifndef AVCODEC_AMR_H
  24 #define AVCODEC_AMR_H
  25
  26 #include <string.h>
  27
  28 #include "avcodec.h"
  29
  30 #ifdef AMR_USE_16BIT_TABLES
  31 #define R_TABLE_TYPE uint16_t
  32 #else
  33 #define R_TABLE_TYPE uint8_t
  34 #endif
  35
  36 /**
  37  * Fill the frame structure variables from bitstream by parsing the
  38  * given reordering table that uses the following format:
  39  *
  40  * Each field (16 bits) in the AMR Frame is stored as:
  41  * - one byte for the number of bits in the field
  42  * - one byte for the field index
  43  * - then, one byte for each bit of the field (from most-significant to least)
  44  *         of the position of that bit in the AMR frame.
  45  *
  46  * @param out pointer to the frame struct
  47  * @param size the size in bytes of the frame struct
  48  * @param data input bitstream after the frame header
  49  * @param ord_table the reordering table as above
  50  */
  51 static inline void ff_amr_bit_reorder(uint16_t *out, int size,
  52                                       const uint8_t *data,
  53                                       const R_TABLE_TYPE *ord_table)
  54 {
  55     int field_size;
  56
  57     memset(out, 0, size);
  58     while ((field_size = *ord_table++)) {
  59         int field = 0;
  60         int field_offset = *ord_table++;
  61         while (field_size--) {
  62            int bit = *ord_table++;
  63            field <<= 1;
  64            field |= data[bit >> 3] >> (bit & 7) & 1;
  65         }
  66         out[field_offset >> 1] = field;
  67     }
  68 }
  69
  70 #endif /* AVCODEC_AMR_H */